Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$74.50	10.687%	$82.4618	$82.46	$82.45	$82.50
Purchase #2	$143.94	10.500%	$159.0537	$159.05	$159.05	$159.10
Purchase #3	$112.37	9.618%	$123.1777	$123.18	$123.20	$123.20
Purchase #4	$118.96	12.164%	$133.4303	$133.43	$133.45	$133.40
Purchase #5	$207.68	5.682%	$219.4804	$219.48	$219.50	$219.50
Purchase #6	$36.55	10.557%	$40.4086	$40.41	$40.40	$40.40
Purchase #7	$250.85	5.789%	$265.3717	$265.37	$265.35	$265.40
7 purchase totals =	$944.85		$1,023.3842	$1,023.38	$1,023.40	$1,023.50